Answer:

SIS

Answer	Crossword Clue
SIS	Auntie, to mom
SIS	Boom preceder, perhaps
SIS	Magda, to Zsa Zsa

SIS	Sib's nickname
SIS	".... Boom Bah" : Heller novel
SIS	Bro's kin
SIS	Cheer starter
SIS	Family member
SIS	Family nickname
SIS	Lorna, to Liza
SIS	Marie, to Donny

SIS	.... boom bah
SIS	.... boom bah (cheer)
SIS	Close relative
SIS	Lisa, to Bart
SIS	See 34A
SIS	Family address
SIS	Lindsay, to Gob and Michael
SIS	Sibling nickname

SIS	Pop sharer?
SIS	Spanish ayes
SIS	Bro's twin
SIS	Sally, to Charlie Brown
SIS	Family member, for short
SIS	Eva, to Zsa Zsa
SIS	What Audrey Meadows calls Jayne?
SIS	Member of the fam

SIS	Shirley, to Warren
SIS	Bro's sibling
SIS	Bro counterpart
SIS	"Boom-bah" lead-in
SIS	Pro votes, in Panama
SIS	One Dionne quint to another
SIS	One of a fam
SIS	Auntie, to Mom, maybe

SIS	Kin of bro
SIS	Malia, to Sasha
SIS	"... boom bah!"
SIS	Family member, briefly
SIS	One of the fam